This invention relates to apparatus for supporting objects of varied shapes for submersion in a liquid, and, more particularly, apparatus for supporting for dip coating foam mold patterns used in a lost foam casting process.
One method of applying a refractory coating to a foam mold pattern is to dip the foam pattern in a refractory coating liquid. This method is often quicker and more efficient than other known methods of applying a refractory coating. However, this method presents a problem in that the foam pattern has a very low density relative to the density of the refractory coating liquid, and therefore the liquid can exert a large buoyant force on the foam pattern. As a result, a substantial force is required to submerge the foam pattern in the refractory coating liquid. Furthermore, the pattern is relatively heavy once it has been coated, and a substantial force is required to lift it from the refractory coating liquid.
Since most foam patterns, and especially those with runner systems, are relatively flimsy, it is desirable, in order to prevent distortion or denting of the pattern, to distribute the stress of the submerging and lifting forces across the pattern as evenly as possible. One way to evenly distribute the stress across the pattern is to provide a rigid fixture that is specially shaped to distribute stress across the particular pattern. Such a rigid fixture is generally usable for only one type of mold pattern, and could not be used for a mold pattern of a different shape. Furthermore, such rigid fixtures are expensive and difficult to build and maintain.
Attention is directed to the following U.S. patents:
Belcher U.S. Pat. No. 4,286,542, issued Sept. 1, 1981; PA1 Porrata U.S. Pat. No. 3,414,502, issued Dec. 31, 1968; and PA1 Caroselli U.S. Pat. No. 2,534,338, issued Dec. 19, 1950.